You’ve probably come across grammar rules like “I before E except after C” and “don’t start a sentence with a conjunction”.
In modern communication, many of these rules are more flexible. Emails often include contractions, informal phrasing and shorter sentence structures.
This raises a practical question for salespeople and marketers: what about capitalization?
In particular, does capital letter use matter in emails? Does it make a difference if we capitalize the first letter of someone’s name or if we stick to lowercase? What happens if we accidentally add a capital letter when typing in a customer’s email address? Will it still get delivered?
In this article, we’ll explore scenarios where capitals do matter and where they don’t. You’ll learn the best practices for using capitalization in emails to make sure your messages get read.
Key takeaways from capital letters in email
Using uppercase letters in email addresses won’t affect where your sales and marketing messages end up.
Although capitalization doesn’t impact email deliverability, it can influence how email content like body copy, subject lines and preheader text is perceived and read.
Best practices for using capital letters in email content include defaulting to natural sentence case, adding numbers to subject lines and pairing with emojis sparingly.
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Do capitals matter in email addresses?
If you’re wondering, “do capital letters matter in email addresses?”, the simple answer here is no. Capitals don’t really matter in email addresses. They aren’t case-sensitive, unlike passwords.
That’s because most modern mail servers see uppercase and lowercase letters as identical.
That means that a message sent to all of these email accounts will reach the same recipient:
The simple answer is no when asking “does capitalization matter in email addresses?” because it is technically possible (though not common) for an uppercase and a lowercase email address to direct to two different mailboxes.
Here’s how it works. Each email address is a combination of two different parts:
The domain name. Everything after the @ symbol (e.g., testemail.com)
The unique address. Everything before the @ symbol (e.g., user93)
The domain part of the email address is entirely case-insensitive, meaning capitals don’t make a difference, ever. If you type GMAIL.COM instead of gmail.com into your browser, your email will end up in the same place.
File Transfer Protocols (FTP) ignore capitalization in domain names and will send your email to the correct mailbox regardless.
With your unique address (the first part of your email, also known as the local part), things get a little more complicated.
Email address case-sensitivity across providers
For emails to be sent and received effectively across various email providers (Gmail, Yahoo, Outlook, etc.), every email provider must adhere to the same email protocol.
Over the last 50 or so years, this set of rules (known as Request for Comments, or RFC) has been revised and updated many times.
The latest version of RFC 5336, an SMTP (Simple Mail Transfer Protocol) extension, states that the first part of an email address (the unique address) can be case-sensitive.
Therefore, theoretically, there may be some servers containing two separate mailboxes for different email capitalizations. For example, [email protected] and [email protected] would direct to different inboxes.
In practice, though, this very rarely happens. It’s really only outdated email servers that use this approach. Virtually every major provider ignores capitalization.
With this in mind, it’s best to stick to lowercase characters when choosing a new email address to avoid any potential problems.
There’s more to email addresses than just case sensitivity, however.
Can you use international symbols in an email address?
In short, yes – email addresses may contain international symbols.
RFC 6530 allows for the following types of international symbols:
Traditional Chinese characters: 喬治@屋企.香港
Latin alphabet with diacritics: jorgé@example.com
Japanese characters: ジョージ@黒川.日本
Greek alphabet: Γεώργιος@παράδειγμα.δοκιμή
Devanagari characters: जोर्गे@डाटामेल.भारत
Cyrillic characters: Джордж@с-балалайкой.рф
However, it’s worth noting that not all email servers will be compliant with RFC 6530.
Outdated RFC 5322 servers won’t be able to handle such addresses. Luckily, you aren’t likely to encounter many outdated servers, since most people use major clients like Gmail and Outlook.
Still, if you’re going to create a mail address with international letters, it may be worth owning a second one using only the Latin alphabet.
For instance, for jorgé@yourdomain.com, you might also create [email protected] and direct it to the same mailbox, so you can still receive emails if senders forget the diacritic.
Can you use numbers in an email address?
Yes, numbers are allowed in email addresses. However, numbers are uncommon in the professional context.
Some larger companies use numbers to delineate between different staff members with the same name (for example, there might be multiple Sarahs at an organization), though best practice is to follow one of these naming conventions:
To maintain a professional appearance, avoid using numerals in place of letters, such as [email protected].
Note: Standardizing email address formats across your organization makes it easier for team members to find and contact each other, especially when reaching out for the first time. As long as the format is consistent, they only need the recipient’s name.
Can you use special characters in an email address?
Only certain special characters can be used in email addresses.
Periods ( . ) and underscores ( _ ) are most common, but the following special characters can also be used:
! # $ % & ‘ * + - / = ? ^ _ ` { | } ~
There are a few other rules around using special characters in an email address:
Periods (or full stops) can’t be used as the first or last letter in an email address (such as [email protected] or [email protected])
The exception to the above is if quotation marks are used (“.yourname”@company.com is acceptable)
You can’t have two periods in a row (e.g., [email protected])
The max length is 64 characters
“ ” ( ) , : ; < > @ [ \ ] are also allowed but with restrictions, since many email servers don’t read them (Gmail addresses, for instance). Best practice is not to use these special characters as they can make an email address harder to remember.
How do email services handle different cases?
The five major services (Gmail, Yahoo Mail, Hotmail, Outlook, Apple Mail) all treat addresses as case-insensitive.
There is no official list of email services that treat email addresses as case-sensitive, and any that still do are outdated and likely to be rarely used.
What characters should I avoid in my email address?
The primary characters that can be used for email addresses are:
Latin letters A–Z
Numerals 0–9
The following special characters: . ! # $ % & ‘ * + - / = ? ^ _ ` { | } ~
Ideally, avoid any other characters when choosing an email address. Not using them will help ensure you can send and receive emails correctly and avoid landing in the spam folder.
6 best practices for using capitalization in email
This article has covered the use of uppercase letters in email addresses. Here’s how to use capitalization effectively in the subject lines and body copy of your sales and marketing emails.
1. Avoid using capitalization in subject lines
Best practice is to avoid overusing capitalization in subject lines. This concerns full caps, as in “THIS IS MY EMAIL SUBJECT LINE”.
While some marketers have A/B tested all-caps subject lines and achieved good results (higher open rates), the downside of this approach is that you risk triggering a spam filter.
Fully-capitalized email subject lines can appear spammy as capitalization is often used as a tool for conveying urgency (a tactic scammers rely on). Therefore, even if your email is legitimate, your customer’s spam filter might decide not to let you through.
2. Test completely lowercase subject lines
On the other hand, writing email subject lines entirely in lowercase (small letters) can be beneficial.
Some marketers find that lowercase subject lines increase email open rates. Others find the opposite.
While, like uppercase subject lines, the jury is still out (i.e., your results may vary), lowercase typically isn’t seen as a spam trigger, so it mitigates the risk of ending up in a spam folder.
However, the potential increase in click-through and reply rates isn’t the only factor to weigh up here.
Some audiences may view the use of lowercase as unprofessional (it is, after all, technically incorrect not to start a sentence with a capital letter). Others may prefer it.
Be careful not to assume that certain demographics, such as younger generations who were raised using the internet and “text-speak”, are less concerned with traditional grammar rules.
The best advice here is to run your own tests.
If lowercase fits within your style guidelines (say, for example, your brand persona is on the casual end of the spectrum), set up an A/B test in your email marketing platform to determine whether or not fully-lowercase email subject lines make a difference with your audience.
3. Use capitalization in emails sparingly
So, do capital letters matter in email addresses? When it comes to the actual body copy in your emails, it’s generally best to use capitalization sparingly.
Most readers would interpret excessive capitalization as shouting, and nobody wants to be shouted at, even by their favorite brand.
This doesn’t mean, however, that you need to avoid capitalization entirely. Uppercase can be used as a way to convey emotion and excitement and to communicate a sense of urgency.
For example, if you’re an e-commerce brand using email marketing to promote an end-of-year sale, a small amount of capitalization in your email content might be appropriate, such as in this email from Designmodo:
Again, your use of capitalization in the email body copy will depend entirely on your brand style guidelines.
4. Use sentence case to appear more approachable
The majority of brands will avoid writing either fully-uppercase or fully-lowercase email subject lines, which leaves you with two options:
Sentence case, as in “This is my email subject line”
Title case, as in “This Is My Email Subject Line”
Title case is typically interpreted as slightly more formal and reads more like a news headline. Sentence case reads more casually.
Your choice to use either title case or sentence case should be based on your brand guidelines. If your goal is to position your brand as serious, formal and professional, title case might be a better solution all around.
If, on the other hand, your goal is to appear more approachable, fun and casual, sentence case might be a better fit.
As sentence case is typically seen as more approachable, the recommendation is to use this style in sales-related emails. You might choose, for example, title case for marketing email communications and investor updates and sentence case for SDR email outreach.
5. Numerals in headlines can increase open rates
It’s well-understood that numerals (0–9) are incredibly powerful tools that, when used in blog headlines, can increase click-through rates several times over.
According to NN Group’s widely cited eye-tracking study, consumers find numerals super compelling, particularly if those numbers are relevant to their current position.
For example, someone struggling with increasing email open rates is very likely to click through on an article titled “How we increased open rates by 73%”, compared to “How to increase email open rates.”
This same logic applies to email subject lines. Where possible, use numerals (rather than spelling out numbers) to improve your own open rates. Some useful examples include:
7 things we learned from our latest product roll-out
We interviewed 3 top sales leaders about account-based selling
Can I book 5 minutes of your time?
What would it mean to reduce your admin costs by 23%?
As with any subject line tactic, test numerals with your audience to see what drives the best results.
6. Use emojis based on your audience
The use of emojis (🙂😂🎉) in emails can be divisive.
Some audiences deem them unprofessional, while others find they help convey tone and make written text easier to interpret.
You’ll likely need to do some testing here and determine how your subscribers and ideal customers feel and whether emojis fit within your brand guidelines.
As a general rule, if your audience is comfortable with a more informal tone, emojis can make email marketing feel more relatable and engaging.
Pipedrive in action: A mix of audience understanding and CRM support helped Swiss software firm TrekkSoft double sign-ups. The company integrated Pipedrive with Mailchimp to scale personalized email outreach with a fraction of its previous effort.
Final thoughts
Do uppercase letters matter in email?
In the case of email address, no, but if we’re talking headlines or email body content, capitalization (or lack thereof) can be an incredibly helpful and subtle tool for influencing open and reply rates.
Remember, it’s all about what works for your audience, so test, analyze, optimize and repeat.
Pipedrive has a suite of tools to help you track and improve email performance. Test them out for yourself with a 14-day free trial.
